Nitric Oxide, a gas that occurs naturally in the body, may do more than any prescription drug to prevent heart attack and stroke. Nitric Oxide is essential for healthy circulation. It helps dilate blood vessels, prevent blood clots and regulate blood pressure. It also helps inhibit the accumulation of dangerous arterial plaque. Nitric Oxide helps prevent heart disease and stroke in the following ways: blood vessels expansion and protecting the blood vessels smooth muscle tissue from harmful constriction. This allows the flexibility necessary for blood to circulate with less pressure. Exercise reduces the risk of a heart attack and protects the heart from injury if a heart attack does occur. For years, doctors have been trying to dissect how this second benefit of exercise works, with the aim of finding ways to protect the heart after a heart attack.

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Researchers at Emory University School of Medicine have identified the ability of the heart to produce and store nitric oxide as an important way exercise protects the heart from injury.Nitric oxide, a short-lived gas generated within the body, turns on chemical pathways that relax blood vessels to increase blood flow and activate survival pathways.

Both the chemical nitrite and nitrosothiols appear to act as reservoirs for nitric oxide in situations where the body needs it, such as a lack of blood flow or oxygen.The Emory team's results, spearheaded by John Calvert and David Lefer, strengthen the case for nitrite and nitrosothiols as possible protectants from the damage of a heart attack.

Nitrosothiols have received much attention in biochemistry because they serve as donors of the nitrosonium ion NO+, and nitric oxide and some organic nitroso derivatives serve as signaling molecules in living systems, especially related to vasodilation. Red blood cells, for instance, release nitrosothiols into the bloodstream under low-oxygen conditions, causing the blood vessels to dilate.

In experiments with mice, the researchers showed that four weeks of being able to run on a wheel protected the mice from having a blocked coronary artery; the amount of heart muscle damaged by the blockage was less after the exercise period. The mice were still protected a week after the wheel was taken away.The researchers found that voluntary exercise boosted levels of an enzyme that produces nitric oxide.

Moreover, the levels of the enzyme stayed high for a week after exercise ceased, unlike other heart enzymes stimulated by exercise. The protective effects of exercise did not last beyond four weeks after the exercise period was over.In mice that lack the enzyme, exercise did not protect the heart from a coronary blockage.Another molecule that appears to be important for the benefits of exercise allows cells to respond to the hormones epinephrine and norepinephrine. All of the beneficial effects of voluntary exercise are lost in mice that are deficient in this molecule. Additional animal studies are currently underway in Lefer's lab to determine the potential benefit drugs that activate this molecule following a heart attack.